The Helsinki airport pods worked well for me.

I was worried about security letting me in the evening before my flight. I arrived about 7pm. In fact, when I put my boarding pass up to a reader at security, red lights flashed and it buzzed. An attendant came over. Tried my boarding pass with the machine, and of course got the same result. Then looked at my ticket and noted that it was for the next morning. I said I had reservations for the GOSleep Lounge. Had the paper reservation in hand, but he didn't bother to look at it. Just said "I will let you in.", and told me it was located at Gate 31.

I found the area actually a little beyond Gate 31 in a secluded corner. There was a sign that the pods were free from 1pm to 9pm. Several of them were occupied, but those people left at various times before 9pm. The free time would be a good way to try them out for a future stay.

There were various models. I'd guess maybe they are testing things. Different pads, some all one piece and some divided where the bed folds to sit up. One with noticeably softer cushion. They look and feel very much like plane lie-flats. In fact they might be. Worth looking them over and picking one with the cushioning of your personal preference.

A bathroom was fairly near the area.

There was no attendant until 9pm. But the young lady that showed up then was very good natured and helpful. Excellent English. Had me sign in just like at a hotel - passport number and other details. Then provided me with a big fluffy pillow, blanket and good ear plugs. The blanket is fleece. It tends to stick to clothing when rolling over, so consequently I would find myself uncovered regularly. Dressing warmly might be a better solution.

The attendant assured me that she would be there all night, so would not let people wander through "that didn't belong there".

There was plenty of room for my carry-on luggage in the space beneath the bed. A lift up of the mattress at the foot of the bed.

I was thinking I'd feel claustrophobic, but didn't. Good ventilation. Fairly quiet over all, and very quiet in the middle of the night.

I woke a couple times in the night, but that is not unusual at my age. In the morning woke easily and ahead of the alarm (5am, with alarm set for 5:30), and felt good. I had an alarm clock, but they will do wake-ups. I had a 7am departure. As it turns out, the gate was only a 5 minute walk away. I easily could have set that alarm clock for 6am.

During Finland's long daylight hours, it might be a good idea to have a sleep mask. A surprising amount of light comes into the pod.

Helsinki airport has free speedy no-password wi-fi. I didn't try the USBs in my pod as I didn't need them, but they were there. However, I did notice some of the pods didn't have USBs, so another reason to check the different models out.

If one is fortunate enough to have appropriate status to get into a lounge, the Finnair/KLM one has showers. I don't know about the other one.

Not an opportunity I'd hunt down, but it will do very well in a pinch. For an early departure, it definitely beats a hotel with a middle of the night checkout, transport, and the now 3-hour-early-arrival required. Also beats airport seating during a long layover.

Somebody asked about the pods being cleaned. They already were very clean and smelled fresh. But while I was there, the attendant spent quite a bit of time with each one, carefully cleaning/sanitizing it. I have to assume it is done every evening before people arrive.